Development of a physical 3D anthropomorphic breast phantom

Abstract

Purpose: Develop a technique to fabricate a 3D anthropomorphic breast phantom with known ground truth for image quality assessment of 2D and 3D breast x-ray imaging systems.

Methods: The phantom design is based on an existing computer model that can generate breast voxel phantoms of varying composition, size, and shape. The physical phantom is produced in two steps. First, the portion of the voxel phantom consisting of the glandular tissue, skin, and Cooper's ligaments is separated into sections. These sections are then fabricated by high-resolution rapid prototyping using a single material with 50% glandular equivalence. The remaining adipose compartments are then filled using an epoxy-based resin (EBR) with 100% adipose equivalence. The phantom sections are stacked to form the physical anthropomorphic phantom.

Results: The authors fabricated a prototype phantom corresponding to a 450 ml breast with 45% dense tissue, deformed to a 5 cm compressed thickness. Both the rapid prototype (RP) and EBR phantom materials are radiographically uniform. The coefficient of variation (CoV) of the relative attenuation between RP and EBR phantom samples was <1% and the CoV of the signal intensity within RP and EBR phantom samples was <1.5% on average. Digital mammography and reconstructed digital breast tomosynthesis images of the authors' phantom were reviewed by two radiologists; they reported that the images are similar in appearance to clinical images, noting there are still artifacts from air bubbles in the EBR.

Conclusions: The authors have developed a technique to produce 3D anthropomorphic breast phantoms with known ground truth, yielding highly realistic x-ray images. Such phantoms may serve both qualitative and quantitative performance assessments for 2D and 3D breast x-ray imaging systems.

FIG. 1.

Orthogonal slices through the breast voxel phantom used as 307 the design of our prototype physical phantom. The sections were made after simulating the breast compression. (a) Axial, (b) coronal, and (c) sagittal phantom slices were made after simulating the breast compression.

FIG. 2.

$R$ of (a) RP and (b) EBR phantom materials as a function of kV. When $R=0$ (indicated by the black line), the phantom materials have the same glandular equivalence as the tissue equivalent materials with known glandular equivalence.

FIG. 3.

(a) Tomographic slice of the voxel phantom composed of fibroglandular tissue, skin, and Cooper’s ligament, corresponding to the slice of the voxel phantom shown in Fig. 1. (b) A 1 cm thick section of the voxel phantom ready for rapid prototyping.

FIG. 4.

(a) Phantom sections of the fibroglandular tissue, skin, and Cooper’s ligaments fabricated using RP in single tissue equivalent materials. (b) Phantom sections after filling the RP printouts with the EBR.

FIG. 5.

(a) DM and (b) reconstructed DBT images of our prototype 3D physical anthropomorphic breast phantom. DM and DBT projection images were acquired with the autofilter AEC technique used for patient imaging. Note the occurrence of air bubbles in the epoxy, seen as radiolucent spheres (arrow).